1. Technical Field
The present invention relates to a recording apparatus in which recording is performed on a recording medium by using a liquid such as ink and, more particularly, to parts that transport and discharge the recording medium on which recording is performed.
In the present application, ink jet type serial printers, line printers, copiers, fax machines and the like are included in the recording apparatus.
2. Incorporated by Reference
The entire disclosure of Japanese Patent Application No. 2013-072490, filed Mar. 29, 2013 is expressly incorporated by reference herein.
3. Related Art
In the related art, ink jet type recording apparatuses are in wide use as this type of recording apparatus. JP-A-2002-326755, JP-A-2005-280214, and JP-A-2011-235494 are examples of the related art. In JP-A-2002-326755, a face-up type structure is used in a part of the ink jet type recording apparatus (hereinafter referred to as “printer”) that discharges the recording medium. In JP-A-2005-280214 and JP-A-2011-235494, face-down type structures are used in parts of the printers that discharge the recording medium.
In the face-up type, the recording medium is discharged to a mounting section in such a manner that a recording surface of the recording medium that is discharged from a discharge section is directed toward the side opposite to a mounting surface of the mounting section where the recording medium is mounted. In the face-down type, the recording medium is discharged to the mounting section in such a manner that a recording surface of the recording medium is directed toward the mounting surface.
In the face-up type printer, when successive printing is performed on a plurality of sheets of the recording medium, tip end sides of the second and subsequent sheets of the recording medium in a transport direction are transported while being in contact with the recording surface of the recording medium which is already discharged to the mounting section and are mounted on the mounting section. Accordingly, deterioration such as unfixed recording contents and images may be generated on the recording surface in a case where ink attached to the recording surface is in a state of not being fixed on the recording surface.
Further, the second and subsequent sheets of the recording medium that are in contact with the recording surface may be contaminated and recording quality may be decreased by the ink which is attached to the tip end sides.
Such problems become further significant due to an increase in recording speed.
Accordingly, in the printer of JP-A-2002-326755, flexibility is added by bending a part of the recording medium so that the tip end side of the recording medium in the transport direction is transported in a non-contact state on the recording surface of the recording medium which is mounted on the mounting section when the recording medium is discharged to the mounting section, is transported to a position substantially right above the recording surface, and then falls to discharge the recording medium to the mounting section.
In this printer, a plurality of discharge rollers are disposed in a width direction crossing the transport direction of the recording medium. In the plurality of discharge rollers, the diameter of the discharge roller that is positioned in a central portion in the width direction is set to be smaller than the diameter of the discharge roller that is positioned on an end section side in the width direction. Also, the coefficient of friction of a surface of the discharge roller that is positioned in the central portion is set to be larger than the coefficient of friction of a surface of the discharge roller that is positioned on the end section side so that a transporting force with respect to the recording medium is uniform in an axial direction of the discharge roller.
In the ink jet type recording apparatus, the recording surface is expanded by absorbing ink drops when the ink drops are attached to the recording surface of the recording medium. When the recording medium is discharged from the discharge section and restriction by a discharge mechanism is released, the recording medium is reversed by the expansion in such a manner that the surface (surface where the ink is not discharged) opposite to the recording surface becomes an inner side, and a left side edge portion and a right side edge portion of the recording medium or a leading edge portion and a trailing edge portion in a front view in the transport direction are curled and deformed. The curling problem also becomes further significant due to an increase in recording speed.
Whether the left side edge portion and the right side edge portion of the recording medium are curled or the leading edge portion and the trailing edge portion of the recording medium are curled depends on the type of the recording medium.
In the printer of JP-A-2002-326755, the recording medium is bent by a plurality of the discharge rollers having different diameters in such a manner that the central portion of the recording surface in the front view in the transport direction is a concave surface more recessed than the left side edge portion and the right side edge portion. The flexibility of the recording medium can be strengthened in the transport direction by forming a recessed surface bending shape (substantially U shape) where the recording surface is the inner side.
However, when the tip end side of the recording medium is separated from the discharge roller and is transported toward the mounting section, a restricting force of the discharge roller does not act on the tip end side of the recording medium and a free state results therefrom.
Also, in this case, the ink drops that are attached to the recording surface are not completely dried. Accordingly, a force to expand and curl the recording medium continues to act on the recording medium. As a result, the recording medium returns to an original flat shape from the tip end side of the recording medium discharged from the discharge section and, further, curling to the side opposite to the recording surface may be caused.
Also, in the face-down type printers of JP-A-2005-280214 and JP-A-2011-235494, the recording medium that is discharged is bent into a substantially U shape with the recording surface being an inner side, that is, a recessed surface and discharge is made in a discharge port section on a downstream side of the discharge roller.
The printer of JP-A-2005-280214 performs recording by forming a regularly wavy shape (cockling) in the width direction of the recording medium crossing the transport direction so as to maintain recording quality of the recording unit. Then, the recording medium is bent into a substantially U shape and discharge is made, with the recording surface being an inner side, by stack levers which are disposed at positions in the discharge port section corresponding to both end sections of the recording medium in the direction crossing the transport direction.
The stack levers in JP-A-2005-280214 are disposed in a rotatable manner. Accordingly, the stack levers bias both of the end sections of the recording medium by using the weight of the stack levers themselves when the recording medium is discharged from the discharge port section. In this manner, the recording medium is bent into a bending shape.
However, the stack levers in JP-A-2005-280214 are in contact with the recording medium at lower ends of a mutually facing side, that is, on a side facing the central portion when the recording medium is bent. In other words, the stack levers are in line contact with the recording medium along the transport direction.
Accordingly, a holding force between the recording medium and the stack levers in the width direction crossing the transport direction is small and thus, even when the bending shape is formed in the recording medium, the bending shape cannot be maintained and the shape is likely to be returned to an original flat state.
Also, in the printer of JP-A-2011-235494, a medium guide is disposed at positions corresponding to both of the end sections of the recording medium in the width direction crossing the transport direction in the discharge port section on a downstream side of the discharge roller. The recording medium is bent into a substantially U shape by the medium guide and is discharged.
Even in the medium guide in JP-A-2011-235494, the recording medium and the medium guide are in a state of being in line contact with each other when the recording medium is bent. Accordingly, even in JP-A-2011-235494, as is the case with JP-A-2005-280214, the bending shape cannot be maintained and the shape is likely to be returned to the original flat state even when the bending shape is formed in the recording medium.